My Heatslave 20/25 has always had a tendency to stop delivering hot water when a tap is running slow. It is fixed by turning tap off then turning on again at a higher flow rate. It has now deteriorated so that it runs out when the shower is used. Presumably the hot water store is depleted then it doesn't feel the need to top up. Delivery of high volume hot water via taps still OK.

David M, November 2010